Electrical switch gear



May 1, 1934. KRlDA 1,957,215

ELECTRICAL SWITCH GEAR Filed Dec. 15, 1933 Inventor:

Hugh Km Patented May 1, 1934 PATENT OFFICE ELECTRICAL SWITCH GEAR Hugh Krida, Upper Darby, Pa., assignor to General Electric Company, a corporation of New York Application December 15, 1933, Serial No. 702,495

6 Claims.

My invention relates to electrical switchgear, more particularly to interlock mechanism for insuring a predetermined sequence of operation in circuit controlling apparatus, as a circuit breaker and isolating or disconnect switching means associated therewith.

The use of interlock mechanism between a circuit breaker and its isolating or disconnect switch for causing tripping of the circuit breaker prior to opening of the disconnect switch is well known and accepted practice. Where a mechanical interlock interconnecting the elements to be interlocked is used, it is desirable that the interlock tripping element be rendered inoperative when the disconnect switch is in either its fully open or closed position without involving complicated or involved mechanism.

A principal object of my invention is the provision of an improved mechanical interlock mechanism of the aforesaid character which shall be simple, inexpensive and rugged in construction and efiicient in operation.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specificaiton.

Fig. 1 is a perspective view, partly in section, of the essential circuit controlling elements of a circuit breaker and associated disconnect switch provided with interlock mechanism embodying the present invention, and Fig. 2 is a detailed view of a portion of the interlock mechanism shown in Fig. 1.

Fig. 1 illustrates in skeleton form electrical switchgear including a circuit breaker 1, associated isolating or disconnect switch 2 and interlock mechanism 3 for insuring proper sequence of operation of the aforesaid switchgear. The circuit breaker 1 may be of any suitable type for interrupting power circuits and as illustrated is of the fluid-break or oil type, comprising a pair of stationary contacts 4 and a movable bridging member 5. The aforesaid contact structure, which is normally immersed in oil, is opened by downward movement of an operating or lift rod 6 connected through a bellcrank 7 and a tripping toggle 8-9 to an operating lever 10. The circuit breaker is of the polyphase type as indicated, but one phase of which is illustrated in the interest of clearness, and opening of the breaker is effected by tripping means acting on the toggle 8--9 from underneath so as to move the toggle joint 9' over center, thereby causing collapse of the toggle, clockwise rotation of the bellcrank '7 and lowering of the bridging member 5 to open the power circuit. The tripping mechanism normally includes a tripping solenoid 11 coacting with a pivoted tripping lug 12 arranged so that actuation of the tripping solenoid causes the lug 12 to strike the toggle joint causing collapse thereof. Closing of the circuit breaker is eifected by first straightening the toggle to its overcenter thrust transmitting position, as shown, where it is held by pin 8' coacting with an extension of link 9, and rotating the operating lever 10 counterclockwise to cause elevation of the bridging member 5.

The lead-in conductor studs 4 of the circuit breaker connected to the stationary contacts 4 are suitably mounted in insulating bushings as illustrated and. form at the upper ends thereof the circuit breaker terminals, each of which is associated with suitable isolating or disconnect switching means indicated at 2.

The disconnect switch 2 comprises in the present instance a pivoted member including a pair of blades 13 arranged to clamp and interconnect the disconnect switch terminals 14 and 15 in the closed circuit position. The blades 13 are pivotally mounted on the terminal 14, as at 16, and are resiliently biased towards each other as by spring washers 17 for making good contact with the stationary terminals. The terminal 14 is electrically connected to a terminal 4 of the circuit breaker by means of a conductor extending through the positioning insulating bushing 18 and conductor strip 19. The opposite terminal 15 is adapted to be connected in the switchgear circuit by conductor 20. The operating means for the disconnect switch 2 comprises a rotatably mounted shaft 21 connected through an insulating toggle 2223 to the switch blades 13. The shaft 21 is connected to suitable operating means as a manually operated handle 24.

The interlock mechanism 3 comprises a. member 25, as a cam, which is connected to the shaft 21 and arranged to coact with the tripping mech anism of the circuit breaker. To this end a member 26 pivotally mounted at 27 is connected to a rod 28 having an oilset extension 28 arranged to engage the tripping lug 2 from beneath so that elevation of the rod 28 causes tripping movement of said lug. The member 26 is likewise pivotally connected, as at 29, to a link 30 which is provided at its outer end with a roller 31 arranged to engage the actuating surface of the cam 25. The link 30 is guided for limited movement as by a pin and slot connection indicated at 32.

Referring more particularly to Fig. 2, the cam 25 is shown as having a pair of actuating faces 33 and 34 generally similar with respect to the center of rotation at 21, and an intermediate portion 35 of greater radius than the cam portions 33 and 34. In the closed circuit position of the disconnect switch the roller 31 engages the cam surface 33 as clearly illustrated in Fig. 1. In this position the rod 28 is in its lower or inoperative position with respect to the tripping lug 12. When, however, the handle 24 of the disconnect switch is initially moved in the circuit opening direction the roller 31 is cammed towards and into engagement with the intermediate cam portion 35 causing clockwise rotation of member 25 and elevation of rod 28 and lug 12 to trip the circuit breaker. Accordingly, the circuit breaker is tripped upon initial opening movement of the disconnect switch and prior to actual opening thereof. In this intermediate position wherein the disconnect switch is neither fully open nor fully closed it is impossible to close the circuit breaker. The disconnect switch is, therefore, protected from damage due to open ing or closing on power currents. Continued rotation of the shaft 21 to the fully open position of the disconnect switch brings the cam portion 34 into engagement with the roller 31 so that the pivoted member 26 is rotated counterclockwise either by the weight of the elements associated therewith or by spring bias, depressing the rod 28 to the inoperative position with respect to the tripping lug 12. The circuit breaker therefore may be opened and closed, as in testing for example, without interference in the interlock mechanism.

Clockwise rotation of the shaft 21 to close the disconnect switch causes elevation of rod 28 and movement of the tripping lug 12 to the tripping position as in movement of the disconnect switch towards open circuit position, the circuit breaker being free to close only when the disconnect switch is closed.

The above interlock mechanism not only involves comparatively few parts but is efficient and positive in. operation in that a direct mechanical connection exists between the disconnect operating shaft 21 and the tripping lug 12 when the disconnect switch is in other than either fully open or closed circuit position.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United is:

1. In electrical switchgear including a circuit breaker and disconnect switching means, interlock mechanism comprising a member arranged to assume different positions in accordance with the circuit-controlling positions of said disconnect switching means, means operatively related to the tripping mechanism of said circuit breaker, and means operatively connecting said member and tripping means for causing tripping of said circuit breaker only when said disconnect switching means is in other than either fully open or closed circuit position.

2. In electrical switchgear including a circuit breaker and disconnect switching means having a rotatable operating shaft, interlock mechanism comprising a member connected to said shaft, means operatively related to the tripping mechanism of said circuit breaker, and means coacting with said tripping means controlled by said member for causing tripping of said circuit breaker only when said disconnect switching means is in other than either fully open or closed circuit position.

3. In electrical switchgear including a circuit breaker and disconnect switching means having a rotatable operating shaft, interlock mechanism comprising a cam connected to said shaft arranged to assume different positions in accordance with the circuit-controlling positions of said disconnect switching means, means operatively related to the tripping mechanism of said circuit breaker, and means coacting with said cam for causing actuation of said tripping means when said disconnect switching means is moved from either its fully open or closed circuit position.

4. In electrical switchgear including a circuit breaker and disconnect switching means having a rotatable operating shaft, interlock mechanism comprising a cam connected to said shaft, and means including a roller coacting with said cam operatively related to the tripping mechanism of said circuit breaker, said cam having an intermediate actuating surface arranged to engage said roller to cause tripping of said circuit breaker when said disconnect switching means is moved from either its fully open or closed circuit position.

5. In electrical switchgear including a circuit breaker and disconnect switching means having a rotatable operating shaft, interlock mechanism comprising a cam connected to said shaft, and means operatively related to the tripping mechanism of said circuit breaker including a pivoted member, and a link connected to said pivoted member having a roller arranged to engage the actuating face of said cam, said cam having a portion arranged to engage said roller to cause tripping of said circuit breaker when said op erating shaft is rotated from either the fully open or closed circuit position.

6. In electrical switchgear including a circuit breaker and disconnect switching means having a rotatable operating shaft, interlock mechanism comprising a cam connected to said shaft, a link having a roller arranged to be in following engagement with the actuating face of said cam, and means operatively relating said link to the tripping mechanism of said circuit breaker, said cam causing tripping of said circuit breaker when said operating shaft is rotated from either the fully open or closed circuit position.

HUGH KRIDA. 

